Preheat oven to 200 degrees Celsius. Cut the mushrooms into cubes, chop the challot onion, chop green onions. Fry the mushrooms in butter, add the challots, saute, add green onion, pour the wine and add the feta, warm until cheese is melted over low heat. In another pan fry in vegetable oil on both sides of the steak with salt and pepper. Share fungal mass on the steak and bake in the oven for 5 minutes.